Apparatus for transporting a floatable marine platform



Feb. 24,1976 LC .P(-DG ONOWISKI ETAI- 3,496,897

APPARATUS FOR TRANSPORTING A FLOATABLE MARINE PLATFORM Filed May 17,1968 States Unite ABSTRACT OF THE DISCLOSURE The invention relates to amethod and apparatus for transporting and launching a deep waterfloatable marine platform. The method embodies the use of at least twofloatable support stages. An elongated marine platform is fioatablysupported on the respective stages, at a plurality of bearing pads orpoints. The stages in turn are spaced apart to permit independentmovement thereof in response to undulations in the body of water. One ormore of the stages are fixedly positioned at one end of the marineplatform, While at least one other stage pivotally supports the oppositeend of said platform to permit the desired independent movement of therespective stages without imposing a strain on the supported platform.

BACKGROUND OF THE INVENTION The usual practice in the construction andtransportation of large marine platforms such as submergible welldrilling platforms, is to build the platform in whole or in parts at ashore installation, and thereafter move the entire unit or units to anoffshore position for anchoring. The two most practical and widely usedways for achieving this include either physically carrying the completedunit to its ultimate location or in the alternative, floating the unitto position. Both methods are desirable under particular conditions.Where the unit is light enough to be carried on barges and within thecapabilities of the available lifting cranes, such transportation isdesirable. However, with bulky and less manageable marine platforms ithas become customary to construct the units in a manner that they willbe self buoyant. Thus, the various members constituting the platformstructure are so arranged and fabricated as to incorporate buoyantchambers which might be controlled to either immerse or float thestructure.

With the present tendency toward relatively deep water installations,the overall size of appropriate marine platforms is becoming steadilylarger. Thus the latter mentioned method of fioatably transporting sucha unit to its working location is preferred. However the drawbacks tothis mode of transportation are similar to those associated with anyland built vessel. The latter for example must be deposited into a bodyof water adjacent to the building site and thereafter floated to itslocation. This of course presupposes that the waterway adjacent to thebuilding site is of a sufficient depth to support the platform as topermit its movement.

For platforms of the type presently considered, the unit when positionedcomprises a singular, large diameter column which extends verticallythrough a body of water from the floor to the surface, and is stabilizedby a base structure. The latter is usually anchored to the ocean floorto fixedly position the entire structure. To adequately and safelysupport an upright column having an order of magnitude of 600 to 1,000feet, it is necessary that the expanse of the base structure must be atleast several hundred feet. It will thus be appreciated that a basemember having for example, a length of approxi- 3,496,897 Patented Feb.24, 1970 mately 400 feet, could not feasibly be floated in a near shorebody of water since the depth would be insuflicient to accommodate theunit.

It is therefore a primary object of the invention to provide a methodand apparatus for supporting and transporting a marine drilling platformbetween its point of fabrication and a submerged working position. A further object is to provide a platform of the type described which mightbe safely launched from floatable support stage or barges in a manner toavoid damaging the platform or the barges. A still further object is toprovide means for facilitating the launching and submerging of a marineplatform whereby the latter is progressively lowered to its ultimateposition while pivotally supported on at least one floatable supportmember. Still another object is the provision of means and apparatus fortransporting a marine platform in a manner to avoid undue stress in thelatter caused by the unsynchronized movement of the floating support inresponse to water undulations.

FIGURE 1 is an elevation view illustrating the invention includingspaced apart fioatable stages supporting an offshore drilling platform.FIGURE 2 is an end view taken line 2-2 in FIGURE 1. FIGURE 3 is asegmentary view on an enlarged scale of a portion of the drillingplatform shown in FIGURE 1. FIGURE 4 is an end view of FIGURE 3. FIGURE5 is a segmentary view on an enlarged scale and in cross section of oneof the stages shown in FIGURE 1, and FIGURE 6 is similar to FIGURE 1illustrating the drilling platform in a partially submerged position.

The present method and apparatus, in brief, affords a convenient meansto safely and economically transport and position a large, floatableoffshore platform. The latter when disposed in an inclined position, issupported at opposed ends by two or more spaced apart stages. Each stageor barge is particularly adapted to permit the platform to ride safelyand securely regardless of water turbulence or undulation. The platformis so received at, at least one end, to loosely engage the sup-portingbarge such that the latter might rock independently of other barges inresponse to movement of the water. Thus, the supported marine platformis not subjected to undue stresses or strain as a result of suddenmovement of the barges.

The apparatus as shown in FIGURE 1, includes essentially a pair ofspaced apart floating stages or barges 10 and 11, each of which supportsa portion of the load comprising marine platform 12. The platform,together with the two stages, might be readily floated through a body ofwater having a depth not substantially exceeding the depth of the stagewhen depressed, without the platform touching the water substratum.Preferably, the respective stages are so arranged that the upwardsupport is provided to the platform at opposed ends. This however is amatter of convenience and the positioning of the stages will be such asto accommodate the particular structure and disposition of the platform.

While the presently illustrated marine platform is adapted to beadequately supported by two spaced apart stages, it is understood thatthe same function can be achieved with three or more stages so arrangedto provide the non-rigid connection between the stages and the platformthus assuring the desired independence of movement.

It is further understood that the marine platform shown and heredescribed constitutes but a single embodiment of the many types of suchplatforms which may be similarly supported and transported. Since mostsuch platforms comprise a plurality of rigidly assembled structuralmembers, the positioning of the stages and bearing joints to provide thedesired freedom of movement, is a matter of practical design. For thepurpose of the following description the marine platform is shown anddescribed to best illustrate the disclosed method, which platform isadapted for immersion in a body of water to be supported on the oceanfloor and a portion above the ocean surface for positioning the usualdrilling equipment and acces sories.

Again referring to FIGURES 1 and 2, the platform is shown in a recliningposition with the normally upright central member at a substantiallyhorizontal attitude. More precisely, the platform comprises an elongatedcentral support column 13 formed of a series of tubular end weldedmembers and being of a substantially uniform diameter throughout. Whenproperly placed for operation, platform 13 extends uprightly from theocean floor to position the top thereof above the water surface.Although not presently shown, the normally upright member 13 may embodyone or more conductor pipes, buoyancy and storage tanks, and similarequipment ancillary to an oil well drilling operation.

Column 13 when in its immersed operating position is maintaineduprightly by a relatively broad base comprising a series of integralstructural members 14, 16, 17 and 18 so arranged and connected to affordthe necessary support to withstand water and wind forces acting againstthe column. A plurality of intermediate reinforcing members 19, 21, 22and 23 connect the lower end of column 13 to the respective basemembers. The column is laterally stabilized at one or more levels byperipherally spaced reinforcing legs, 24 and 26 for example, whichextend from the base, and are fastened to the outer wall of column 13.

Following usual construction techniques, the various structural membersof the platform including the base and the legs are joined by welding.They are further provided as above noted, with controllable buoyancymembers such as tanks built into the various members and so connected topiping means to regulate the condition of the tanks and consequently theattitude of the platform when in the water.

As shown in FIGURES 1 and 3, the upper end of column 13 is provided withan arm or brace assembly 27 which is fastened to the column primarily asa temporary expedient for transporting the platform. After use, theassembly may be either removed, or left in place in anticipation of asubsequent move. Arm assembly 27 includes basically a plurality ofcompression elements 28 and 29 which are end welded or otherwise affixedto the outer wall of column 13 and extend therefrom. The remote ends ofthe respective compression elements terminate in a joint 31 such as abearing knuckle 31, anvil or similar member having a contoured undersideadapted to slideably engage a complementing seat. The arm structure maybe further provided with a guide brace 32, formed in a generally arcuateshape and fastened at one end adjacent to knuckle 31 and at the otherend to the column 13. The respective compression and arcuate members 28,29 and 32 as shown in FIGURE 4 are split, or assume a general Vconfiguration having the extremities fastened to opposed outer walls ofcolumn 13 and terminating at knuckle member 31. Arm or brace assembly 27might be welded or bolted to the outer wall of column 13, the latter isin turn reinforced by plates or circular bands 25 to accommodate anddistribute the load concentration on column 13 when pivotally supportedat arm 27.

Floatable stages or barges 1t) and 11 supporting platform 12, by andlarge follow the normal construction for such units and comprise inessence a relatively expansive tank embodying buoyant means forcontrollably varying the level and attitude thereof in a body of water.For example, stage is so positioned to support the base structure of themarine column, in a rigid or semirigid manner to permit, althoughminimize movement of the column with respect to said barge. Thus basemember 17 might be rigidly secured to barge 10; alternately it might beso supported in a manner to permit movement of the stage in response towater undulations. Lower element 17 of the base assembly is supportedwith the latter positioned approximately adjacent to the bottom of stage10. In such a position, while being transported, the marine platform maybe at least partially submerged thereby af fording a degree of selfsupport.

Stage or barge 10 may as mentioned, be provided with internal buoyancycontrol such that the flooding of discrete chambers will regulate therate of descent and attitude of the stage as well as of the platform toenhance the seaworthiness of the unit. In the present arrangement, asingle fioatable stage 10 is utilized to support the lower or heavierend of the marine platform 12. This support can be supplemented withother similar stages should the length of member 17, or the physicalsize of the stage warrant additional floating support.

Barge 10 is provided with an articulated support as sembly such as 50which pivotally attaches to the lower part of the stage underside as byan elongated hinged joint 51. Said assembly 50 comprises essentially apair of arms 52 disposed on opposed ends of the stage. While a singlearm is here shown in the figures, it is understood that a correspondingarm assumes a similar position on the opposite end of the stage suchthat both arms of the assembly work simultaneously. Each arm is rigidlyconnected at the lower end to a pivotal hinge such as pin 51. The remoteend of each arm is further provided with a cradle 53 or similarreceptive member adapted to receive and support one end of the marineplatform 12.

Cradle 53 for example may include a journal surface positioned in directcontact with the member to be supported. Thus, when the latter is of acylindrical shape, an upper clamping bracket 53 grasps the platformmember firmly in a rolling grip and yet allows the barge to pitch orroll slightly in response to undulated movement of the water.

The entire arm assembly 50 is preferably connected to a suitable sourceof power to be operated as a unit, whereby the arms may be pivoted aboutpin 51 to adjust position of the supported end of the platform in thewater. However, each arm may also be individually powered and controlledto be operated with respect to the stage.

Stage 11, positioned remote from stage 10 is similar in basicconstruction to the latter. Stage 11 however incorporates the additionalfeature of being so adapted to embody a seat 33 or socket whichcooperates With a corresponding bearing pad of the platform to permit ineffect limited universal movement between the two.

Seat 33 is adapted to receive anvil 31 or other appropriate form ofbearing pad. Said seat includes upstanding side walls 34, 36 definingthe seat outer edge, which side walls may be tapered inwardly to readilyreceive and guide anvil 31 as the latter is lowered into place onto thestage. As shown in the figures, the entire seat 33 within stage 11 ispositioned at a low level in the stage or barge preferably such that theseat itself is below the center of buoyancy of the barge thus providingthe latter with a substantial degree of stability under heavy loadingconditions.

To properly function as the journal surface for bearing pad 31 extendingfrom the platform 12, seat 33 comprises primarily a foundation orcontact surface which may be adapted to provide either a smooth surface,or a pliable cushion type surface.

In the instance of the smooth surface the contoured face of thefoundation includes a metallic foundation block 37 having an upwardfacing, contoured opening conforming to the contoured face of the anvil31. As the latter is seatably positioned in the foundation block,movement of either the platform 13 or barge 11, results in a slidingrelationship between the anvil and its mating contoured seat, thusproviding maximum bearing along the contoured face of the anvil incontact with the foundation block 37.

In an alternate embodiment of the foundation member not presently shown,the latter may be provided with a layer of displaceable material such asstone aggregate, gravel or the like which will sufficiently yield underthe pressure of the contoured anvil 31 to form a seat of the propershape.

The relationship of anvil 31 within seat 33, whether the latter be ofthe smooth contoured type or of the cushion type, is to permit in effectlimited universal sliding movement of the anvil in the seat. This actionpermits the platform to move or adjust independently of the undulationsof any one support stage or barge 11 as the latter is subject tomovement of the water.

To permit automatic effective adjustment of platform 13 on therespective supporting stages and 11, the slideable connection betweenthe latter and the bearing pads is supplement with restraining lines 39and 41. The tension in such restraining lines is such as to permit thedesired limited movement, and yet prohibit the stage from beingdisplaced entirely from its supporting relationship with the platform asthe stage is towed.

The nature of the sliding joint formed between anvil 31 andcorresponding seat 33 is such as to provide a minimum degree of frictionbetween engaging members and allow the desired freedom of movement.Thus, anvil 31 particularly at the lower curved face may comprisereplaceable metallic convex shoes or wear surfaces. This wear surface isapplied to a rigid contoured body such as a hemispherical shape formedof a steel shell, which in turn attaches to the respective compressionmembers 28 and 29.

The seat or foundation block 41 upon which anvil 31 bears may be adaptedas previously mentioned for forming a pliable cushion into which theanvil might work itself while being lowered into position. Alternately,the foundation block 41 may be lined, as is shoe 31, with a metallicmaterial either in strip form or as a solid metallic sheet. In theinstance of the latter the sliding relationship between the contactingmembers might be improved by use of a suitable lubricant such as a heavygrease injected between the faces of the anvil 31 and its foundationblock 37 to form a thin lubricating layer.

It will be appreciated that under ordinary conditions wherein theplatform is being either towed at sea, or merely standing in a body ofwater, the engaging surfaces of anvil 31 and its seat will be in avirtually continuous state of relative movement. Thus the rigid typesurface joint embodies certain advantages since the deformable orpliable cushion type seat which will tend to be displaced under thegreat weight of the platform assembly thereby presents the possibilityof Wearing away or displacing entirely the pliable cushion.

From the foregoing it is seen that the present arrangement suggests manyadvantages in the transportation and the setting of an offshore typeplatform in either deep or shallow water. The number and the positioningof the bearing pads will of course be contingent on the particular sizeand shape of the platform. For example bearing pads 37 and 38 in thepresent instance are located preferably at opposed ends of base supportmember 17 While a third bearing pad is located at the terminus ofcentral column 13. Thus, the structure is ideally supported by bearingpads spaced apart to provide a triangular form of three point support.This type support of course is the most stable and the least likely toimpose stress on the platform being supported.

In the instance of a platform utilizing two, three or more legs, thelatter might be provided with a suitable bracing arrangement to maintainthe single point of sup port at one end of the platform.

It should also be appreciated that the number of stages utilized forsupporting a platform most efficiently and with the least strain imposedon the latter, would be contingent on the dimensions of the platformbase, or the width of the entire platform. For example on a relativelysmall unit, conceivably two stages might be readily utilized, one beingsupportably positioned beneath the platform base while a second platformis disposed at the upper terminus of the platform. Where of course thebase is of sufficient width to warrant more than one stage or supportbarge, each of the latter will move independently one of the otherthereby continuing the three point support and the minimization of thestrain on the supported platform.

Further, the description has heretofore disclosed the novel arrangementin terms of the upper bearing pad or anvil 31 as 'being the soleconnection adapted to universal movement in response to undulations ofthe water. However this does not preclude the use of a similar supportpoint or bearing pad at each of the points at which the platform issupported. Each of the support stages might be provided with a recessedseat as described with respect to stage 11 to receive an anvil-likebearing pad.

In the actual practice of the method and the apparatus used therefor,platform 12 is normally constructed on land and thereafter eitherpartially or completely floated onto one or more of the supportplatforms as herein noted. In the instance of a single column elongatedplatform as shown in the figures, the width or length of the base wouldordinarily preclude the entire platform from being floated in the waterprior to being put on the supporting stages. Therefore transfer of theplatform to the respective support stages is achieved while the platformis on the land at the construction site.

It should be further appreciated that the various bearing points of theplatform are so arranged and positioned to provide a relatively uniformweight distribution between the respective stages to facilitate both thetransportation and the subsequent handling of the platform.

In the instance of an elongated type platform as presently shown,maximum utilization of the water buoyancy might be achieved by at leastpartially immersing a portion of the platform base to provide a degreeof buoyancy to supplement the buoyant effect of the respective supportstages. In such position, the platform will receive maximum self-supportand thereby avoid the possibility of straining of the platform centralcolumn when the latter is supported at its terminals.

In the instance of the upper, or bearing pad adjacent at the top ofcolumn '13, the base end is elevated above the stages 10, or the latterare submerged and then floated to rise beneath the base bearing pads.Thereafter, the platform upper end is raised to align anvil 31 over seat33, thence lowered into place. When so positioned the respectiveretaining lines at the joints are adjusted to maintain the stages andbearing pads in the proper engaged position and yet permitting thedesired freedom of movement therebetween.

As used in the above description, the terminology first and secondstages refers of course to the support members which are fioatable andsimilarly submergible, characteristic of a barge having controlledbuoyancy features. Further, the terminology bearing pad relates to theparticular balance points within the platform structure which, whensupported, will permit the platform to be transported in the most stableand controllable manner.

With respect to disengaging agent of the platform for the bearing pads,at a desired offshore platform site, the platform is preferably loweredinto place to rest the base on the ocean fioor. By controlling thebuoyancy of the platform, column 13 will be maneuvered into asubstantially upright position with the upper end of column 13 extendingabove the water surface.

With the platform so positioned, anvil 31 or arm assembly might beremoved or alternately left in place depending on the position of thesame with respect to the normal platform accessories which will besupported at the upper end of the column such as the derricks,draw-works, storage facilities, etc.

Obviously many modifications and variations of the invention as hereinset forth may be made without departing from the spirit and scopethereof.

We claim:

1. In the waterborne transport and positioning of an elongated offshoremarine platform within a body of water, said platform being formed of atleast one elongated member having opposed ends, and being normallydisposed for operation in a substantially upright attitude Within saidbody of water;

a first stage element fioatably supporting one end of said elongatedmarine platform at at least one bearing pad,

a second stage element fioatably supporting the opposed end of saidplatform at another bearing pad spaced from said first mentioned bearingpad,

said bearing pads on said elongated platform being each operably engagedwtih a corresponding support element, each element of which includes aseat adapted to receive a bearing pad to permit restrained pivotalmovement of said pad on said seat,

at least one of said bearing pads including a brace depending from saidplatform elongated member and an anvil carried at the remote end of saidbrace, said anvil being operably received on said floating supportelement,

whereby said platform is maintained by said terminal support in asubstantially horizontal disposition at the waters surface, whileavoiding imposition of undue physical strain into said platform as theresult of movement of said respective support elements in response towater undulations.

2. In the waterborne transport and positioning of an elongated offshoremarine platform within a body of water, said platform being formed of atleast one elongated member having opposed ends, and being normallydisposed for operation in a substantially upright attitude within saidbody of water;

a first stage element fioatably supporting one end of said elongatedmarine platform at at least one bearing pad,

a second stage element fioatably supporting the opposed end of saidplatform at another bearing pad spaced from said first mentioned bearingpad,

said bearing pads on said elongated platform being each operably engagedwith a corresponding support element, each element of which includes aseat adapted to receive a bearing pad to permit restrained pivotalmovement of said pad on said seat,

at least one of said bearing pads including a brace depending from saidplatform elongated member, and

an anvil carried at the remote end of said brace, said anvil beingoperably received on said fioatably supporting stage element, saidlatter mentioned support element including a seat defined by upstandingwalls and a foundation member, said anvil being disposed in said seatand in sliding engagement with said foundation member,

whereby said platform is maintained by said terminal support in asubstantially horizontal disposition at the waters surface, whileavoiding imposition of undue physical strain into said platform as theresult of movement of said respective support elements in response towater undulations.

3. In an apparatus as defined in claim 2 wherein said foundation memberincludes a substantially solid block contoured in accordance with thecontour on said anvil, whereby said anvil when disposed in saidfoundation block defines a bearing area across the face of said anvilregardless of the relative positions thereof in said foundation block.

4. In an apparatus as defined in claim 3 wherein said foundation blockand said anvil are similarly contoured to define a bearing area acrossthe face of said anvil regardless of the relative position thereof insaid foundation block.

5. In an apparatus as defined in claim 2 wherein said latter mentionedfioatable supporting stage includes a seat defined by upstanding Wallsand a foundation base, said foundation base including a pliable cushionformed of a material adapted to being displaced and assuming the contourin said displaced position of said anvil face when the latter isoperably engaged with said seat.

6. In an apparatus as defined in claim 2 wherein at least a portion ofthe upstanding walls of said seat are inwardly tapered to a conjunctureat the said seat.

7. In an apparatus as defined in claim 2 wherein said seat for receivingsaid anvil is positioned at a depressed location in said floatablesupport stage at a point below the center of gravity of said stage.

References Cited UNITED STATES PATENTS 2,581,098 1/1952 Guenzel 6146.53,323,478 6/1967 Hunsucker 114-.5 3,347,052 10/1967 Steitle et al. 114.5

TRYGVE M. BLIX, Primary Examiner U.S. Cl. X.R. 6146.5

